EP0004476A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Time base error correction for optical disc players
Assignee: Discovision Associates
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Filing: 1979-03-27
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Granted: —
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Expires: 1999-03-27
Abstract
Abstract An optical apparatus is described for use with a video disc (7) having frequency modulated video information (9) recorded thereon in the form of a plurality of concentric circles or a single spiral. The information track comprises successively positioned light reflective and light non-reflective regions (10, 11). A focused light beam (4) is caused to be positioned over the centre of an information track and the light reflected from the information track is gathered by an objective lens (17) for application to electronic circuitry (30) for recovering the recorded frequency modulated video signals. Radial tracking means are described for maintaining the focused light spot to impinge upon the centre of an information track. Lens focusing means are described for positioning the objective lens at the optimum focused position above the information track for gathering the maximum amount of reflected light from the information track. FM processing means are described for reconstructing the recovered frequency modulated video information such that the ratio between the amplitude of the signals as recorded is essentially the same in the signals as recovered from the video disc member. Further servo means are described for handling the selective change of the intersection of the reading beam with the video disc member in a predetermined preferred mode of operation.
Inventors
- 👤 Ludwig Ceshkovsky
- 👤 Wayne Ray Dakin
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 14:05
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B19/00; G11B19/20; G11B19/28; G11B21/00; G11B21/02; G11B21/10; G11B7/004; G11B7/005; G11B7/08; G11B7/085; G11B7/08505; G11B7/08511; G11B7/09; G11B7/0941; G11B7/0908
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
67 words
Optical apparatus comprising a lens arranged when focussed on an information bearing surface, to collect from the surface radiation modulated in accordance with the infbrmation including a driver arranged to drive the lens towards and away from the. surface, and means responsive to the collected radiation when the lens is not focussed on the surface to operate the driver to drive the lens to a focussed position.
Claim 2
Dependent Claim
67 words
Optical apparatus comprising a lens arranged when focussed on an information bearing surface, to collect from the surface radiation modulated in accordance with the infbrmation including a driver arranged to drive the lens towards and away from the. surface, and means responsive to the collected radiation when the lens is not focussed on the surface to operate the driver to drive the lens to a focussed position.
Claim 3
Dependent Claim
120 words
2, A focussing method for use in a player apparatus for deriving information from an information bearing surface, said player apparatus including optical means for directing. a source beam of.radiation along a prescribed optical path to said surface, said method comprising the steps of; directing the source beam through an objective lens means onto the information bearing surface; detecting the position of said objective lens means relative to the information bearing surface; driving said objective lens in a first direction through a predetermined range of travel that includes an optimum focussing position, and intermittently driving said objective lens in a direction opposite to said first direction, whereby said lens driver means scans back and forth past said optimum focussing position.
Claim 4
Dependent Claim
120 words
2, A focussing method for use in a player apparatus for deriving information from an information bearing surface, said player apparatus including optical means for directing. a source beam of.radiation along a prescribed optical path to said surface, said method comprising the steps of; directing the source beam through an objective lens means onto the information bearing surface; detecting the position of said objective lens means relative to the information bearing surface; driving said objective lens in a first direction through a predetermined range of travel that includes an optimum focussing position, and intermittently driving said objective lens in a direction opposite to said first direction, whereby said lens driver means scans back and forth past said optimum focussing position.
Claim 5
Dependent Claim
157 words
A focus servo system for use in a player apparatus for deriving information from an information bearing surface, said player apparatus including optical means for directing a source beam of radiation along a prescribed optical path to said surface, said focus servo system comprising; objective lens means for focussing the source beam on the information bearing surface; and control means coupled to said objective lens means for selectively driving said objective lens means to an optimum focussing position, said control means including a ramp signal generator for generating a ramp signal for driving said objective lens means in a ramp fashion toward said information bearing surface from a retracted position, said control means further including a kick-back generator for generating an oscillatory waveform for driving said objective lens means in a reciprocating movement about said optimum focussing position, said oscillatory waveform commencing at a fixed time after initiation of said ramp signal by said ramp signal generator.
Claim 6
Dependent Claim
157 words
A focus servo system for use in a player apparatus for deriving information from an information bearing surface, said player apparatus including optical means for directing a source beam of radiation along a prescribed optical path to said surface, said focus servo system comprising; objective lens means for focussing the source beam on the information bearing surface; and control means coupled to said objective lens means for selectively driving said objective lens means to an optimum focussing position, said control means including a ramp signal generator for generating a ramp signal for driving said objective lens means in a ramp fashion toward said information bearing surface from a retracted position, said control means further including a kick-back generator for generating an oscillatory waveform for driving said objective lens means in a reciprocating movement about said optimum focussing position, said oscillatory waveform commencing at a fixed time after initiation of said ramp signal by said ramp signal generator.
Claim 7
Independent Claim
168 words
A method of time base error correction for use in an apparatus for deriving information from tangentially arranged information tracks on a surface of a disc wherein said information includes a synchronizing signal, said apparatus, including optical system means for impinging a source beam of radiation upon said information tracks at a selected location to produce a modulated beam of radiation containing said information, and signal recovery means for recovering said information from said modulated beam and for producing an electrical signal representative of said information, said method comprising the steps of; separating said synchronising signal from said information in said electrical signal; generating a reference signal having a prescribed frequency; detecting the relative phase between said synchronising signal and said reference signal generating a control signal representative of the detected phase difference therebetween; and moving the impingement location of the source beam along the information tracks as a function of said control signal, whereby the phase difference between said synchronising signal and said reference signal is reduced.
Claim 8
Independent Claim
168 words
A method of time base error correction for use in an apparatus for deriving information from tangentially arranged information tracks on a surface of a disc wherein said information includes a synchronizing signal, said apparatus, including optical system means for impinging a source beam of radiation upon said information tracks at a selected location to produce a modulated beam of radiation containing said information, and signal recovery means for recovering said information from said modulated beam and for producing an electrical signal representative of said information, said method comprising the steps of; separating said synchronising signal from said information in said electrical signal; generating a reference signal having a prescribed frequency; detecting the relative phase between said synchronising signal and said reference signal generating a control signal representative of the detected phase difference therebetween; and moving the impingement location of the source beam along the information tracks as a function of said control signal, whereby the phase difference between said synchronising signal and said reference signal is reduced.
Claim 9
Independent Claim
186 words
A method of signal correction for use in a player apparatus for deriving information recorded on an information bearing surface wherein said recorded information occupies a frequency spectrum and includes a reference signal of prescribed amplitude in a first portion of said frequency spectrum, said player system including an optical system for directing a modulated beam of radiation containing said information from a selected location on said information bearing surface to a signal recovery system wherein an electrical signal representation of said modulated beam is derived, said optical system having a nonuniform gain characteristic over a second portion of said frequency spectrum that excludes said first portion said signal correction method comprising the steps of; separating said reference signal from the remainder of said electrical signal; comparing the amplitude of said reference signal with a predetermined amplitude adjusting the amplitude of said electrical signal over said second portion of said frequency spectrum as a function of the difference in amplitude between said reference signal and said predetermined amplitude whereby the effects of said nonuniform gain characteristics of said optical system on said modulated beam are reduced.
Claim 10
Independent Claim
186 words
A method of signal correction for use in a player apparatus for deriving information recorded on an information bearing surface wherein said recorded information occupies a frequency spectrum and includes a reference signal of prescribed amplitude in a first portion of said frequency spectrum, said player system including an optical system for directing a modulated beam of radiation containing said information from a selected location on said information bearing surface to a signal recovery system wherein an electrical signal representation of said modulated beam is derived, said optical system having a nonuniform gain characteristic over a second portion of said frequency spectrum that excludes said first portion said signal correction method comprising the steps of; separating said reference signal from the remainder of said electrical signal; comparing the amplitude of said reference signal with a predetermined amplitude adjusting the amplitude of said electrical signal over said second portion of said frequency spectrum as a function of the difference in amplitude between said reference signal and said predetermined amplitude whereby the effects of said nonuniform gain characteristics of said optical system on said modulated beam are reduced.
Claim 11
Dependent Claim
104 words
A tracking system for use in a player for deriving information from a surface of a disc, said player including optical means for directing a source beam of radiation along a prescribed optical path to said surface, said tracking system comprising carriage means for translating the disc relative to the optical means at a selected translation rate; mirror means for adjusting the path of the source beam relative to the optical means; said mirror means having an optimum range of adjustment, and tracking error detection means, generating an error output to said mirror means for controlling adjustment of the path of the source beam.
Claim 12
Dependent Claim
104 words
A tracking system for use in a player for deriving information from a surface of a disc, said player including optical means for directing a source beam of radiation along a prescribed optical path to said surface, said tracking system comprising carriage means for translating the disc relative to the optical means at a selected translation rate; mirror means for adjusting the path of the source beam relative to the optical means; said mirror means having an optimum range of adjustment, and tracking error detection means, generating an error output to said mirror means for controlling adjustment of the path of the source beam.
Claim 13
Dependent Claim
170 words
A spindle servo system for use in an apparatus for deriving information from an information bearing surface of a disc, said apparatus including an optical system means for directing a source beam of radiation to said surface of said disc and for directing a modulated beam of radiation containing said information from said surface of said disc to a signal recovery system, said spindle servo system comprising; spindle motor means for rotating said disc, spindle tachometer means for producing a spindle tachometer signal with a frequency indicative of the angular rate of rotation of said spindle motor means; spindle reference signal means for producing a spindle reference signal with a frequency representing a desired angular rate of rotation of said spindle motor means, and phase detection means for detecting the relative phase between said spindle tachometer signal and said spindle reference signal, and for generating a spindle motor control signal representative of the detected phase differences therebetween to drive said spindle motor means at said desired angular rate of rotation.
Claim 14
Dependent Claim
170 words
A spindle servo system for use in an apparatus for deriving information from an information bearing surface of a disc, said apparatus including an optical system means for directing a source beam of radiation to said surface of said disc and for directing a modulated beam of radiation containing said information from said surface of said disc to a signal recovery system, said spindle servo system comprising; spindle motor means for rotating said disc, spindle tachometer means for producing a spindle tachometer signal with a frequency indicative of the angular rate of rotation of said spindle motor means; spindle reference signal means for producing a spindle reference signal with a frequency representing a desired angular rate of rotation of said spindle motor means, and phase detection means for detecting the relative phase between said spindle tachometer signal and said spindle reference signal, and for generating a spindle motor control signal representative of the detected phase differences therebetween to drive said spindle motor means at said desired angular rate of rotation.
Claim 15
Dependent Claim
97 words
An optical system for use in a player for deriving information from a surface of a disc, said player including a beam source of energy radiation for impinging upon said surface, and a signal recovery system for receiving from said surface a modulated beam of radiation containing said information, said optical system comprising; lens means between said disc and said signal recovery system, said lens means having a resolution value which limits the passage of higher frequency components of said modulated beam of radiation, said lens means thereby defining a low pass filter for said modulated beam.
Claim 16
Dependent Claim
97 words
An optical system for use in a player for deriving information from a surface of a disc, said player including a beam source of energy radiation for impinging upon said surface, and a signal recovery system for receiving from said surface a modulated beam of radiation containing said information, said optical system comprising; lens means between said disc and said signal recovery system, said lens means having a resolution value which limits the passage of higher frequency components of said modulated beam of radiation, said lens means thereby defining a low pass filter for said modulated beam.
Claim 17
Dependent Claim
118 words
A tracking system for use in a player for selectively deriving information from any of a plurality of spaced information tracks on an information bearing surface said apparatus including optical means,for producing a source beam of radiation to impinge upon said surface and moving means for moving said surface relative to said source beam for causing said beam to scan said surface along any one of said tracks, said tracking system comprising beam steering means for steering the source beam along a path defined by a first information track, and control means, coupled to said beam steering means, for selectively conditioning said steering means to redirect the source beam along a path formed by a second information track.
Claim 18
Dependent Claim
118 words
A tracking system for use in a player for selectively deriving information from any of a plurality of spaced information tracks on an information bearing surface said apparatus including optical means,for producing a source beam of radiation to impinge upon said surface and moving means for moving said surface relative to said source beam for causing said beam to scan said surface along any one of said tracks, said tracking system comprising beam steering means for steering the source beam along a path defined by a first information track, and control means, coupled to said beam steering means, for selectively conditioning said steering means to redirect the source beam along a path formed by a second information track.
Claim 19
Dependent Claim
103 words
A control system for use in a video disc player for deriving information from a video disc having an information bearing surface said player comprising optical means for reading information stored on said disc, a spindle servo system for rotating said disc at a controlled rate; and a carriage servo for translating said disc relative to said optical means responsive to any one of a plurality of command signals, said carriage servo translating said disc from an initial standby position to a play position responsive to an output from said spindle servo indicating that said disc is rotating at a predetermined angular rate.
Claim 20
Dependent Claim
103 words
A control system for use in a video disc player for deriving information from a video disc having an information bearing surface said player comprising optical means for reading information stored on said disc, a spindle servo system for rotating said disc at a controlled rate; and a carriage servo for translating said disc relative to said optical means responsive to any one of a plurality of command signals, said carriage servo translating said disc from an initial standby position to a play position responsive to an output from said spindle servo indicating that said disc is rotating at a predetermined angular rate.
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